Mazel tov to Facebook founder Mark Zuckerberg and his longtime girlfriend, med student Priscilla "Cilla" Chan, who are engaged! According to Bill Gates, at least, who seemed to let the news slip during an interview with The Daily Mail:

He is friends with Facebook founder Mark Zuckerberg, 27, who has already pledged to give most of his fortune away. Gates lets slip that Zuckerberg may be engaged to Priscilla Chan, his long-term girlfriend: ‘I didn't say to Mark, "Give me all your money!" He was predisposed to do it and he came to me seeking advice.

'His fiancée Priscilla thought about education and he gave money to Newark, New Jersey, and we did a co-grant so that some of our people who had some expertise in that field could help him out.

We checked with Facebook's head of communications, Elliot Schrage, who suggested that Bill Gates was mistaken. "If [Mark is engaged, Bill Gates] knows something I don't know. Gates's communications guy just wrote to apologize for the misunderstanding."

On the one hand, calling Chan Zuckerberg's fiancee is an understandable, even likely, slip. On the other hand, we'd probably tell Bill Gates about our engagement before Elliot Schrage. No offense, Elliot.